CYMK conversion

[Kees Sprengers]

My wife and i have been working for the past years been working on producing a cookbook about Norther Laos food.

I produced the bulk of the photographs, some taken as long as 7 years ago on a Sony 717, later the 828, The Canon 20D, then 5d, now 5D Mk11.
Progression in quality. From the 5D onwards, I used RAW, before that jpg. All taken in situ, often badly lit local kitchens, sometimes bamboo huts by oil lamp light. In short, a mixed bag in terms of quality.

About a year and a half ago, she started doing the layout in InDesign, aiming to have the book printed online via Lulu or Blurb. Lulu indicated sRGB was Ok for their printing process.

Each of the 350 photographs in the book was processed by me, usually in Lightroom, occasionally in PS CS3. Then exported into jpg sRGB, sized for the final size in the book and 300 ppi, using the LR export function. This helped us reduce the total size of the book in terms of MB, rather then using the original jpg size, sometimes 14 mb each.

We received a sample copy from the printer, and weren't happy with the print quality, the bind (glue) fell apart rapidly, and the prices had escalated since we first investigated the process. So we decided instead to go to offset print, and print in Thailand, where we live, using a local Bangkok printer who has shown us previously printed books of good quality.

During our talks yesterday, they reminded us that they prefer to receive it in the inDesign format, but with all photographs in CYMK.

Since I didn't keep my export settings for each image on file, I have two options:
1. the lazy way, opening each exported (already sized for the book and usually reduced) jpg in PS, resaving it some size in CYMK.

Risk, resaving jpg can cause loss of quality.

2. Going back to each original image (still in a LR catalogue, exporting it from LR to PS, opening it, resize to required size for the book, change ppi to 300, export as jpg CYMK.

Because I'd be using the original file (RAW or jpg), tweaked in LR, I'd also have to apply each crop again accurately as chosen in the layout.

The total amount of work will be a lot more, since she will probably have to re-align each image again in the layout. in InDesign.


My Question: Is step one e.g., open and re-save jpg in CYMK adequate, or would I be better to use step 2 and start from scratch?

[papa v2.0]

hi
from a pre press background

I would first ask the printer if you can supply the work as a pdf.

if so you can get the icc profile of the press (or the profile they would recommend to separate to cmyk) and do the conversion from srgb to cmyk when you export from indesign to pdf.


or batch convert in ps and save as tiff and auto update( relink the file) in indesign. (again you need the appropriate cmyk profile or settings)

[Ken Bennett]

We supply 8-bit TIFF files in CMYK to our printers on the high end jobs. If you open your sRGB JPEG, convert it to the appropriate CMYK profile for the press conditions, then save it as a TIFF, you won't lose any quality due to re-compression of the JPEG.

If you can't get a specific press profile from the printer, the stock CMYK profiles in Photoshop are quite good. Just choose the paper and press conditions (sheet fed coated, for example) and get proofs.

You could, in theory, get somewhat better color by starting with the raw files, and working through a wide-gamut RGB color space before the conversion to CMYK. However, in reality, working with sRGB files works just fine 99% of the time. (There are so many other variables in the offset printing process....)

--Ken

[Kees Sprengers]

hi
from a pre press background

I would first ask the printer if you can supply the work as a pdf.

if so you can get the icc profile of the press (or the profile they would recommend to separate to cmyk) and do the conversion from srgb to cmyk when you export from indesign to pdf.


or batch convert in ps and save as tiff and auto update( relink the file) in indesign. (again you need the appropriate cmyk profile or settings)

>if so you can get the icc profile of the press (or the profile they would recommend to separate to cmyk)<
Printer prefers a inDesign format.

Trying to get the recommended CYMK profile out of them, but struggling with language issues.

>do the conversion from srgb to cmyk when you export from indesign to pdf.<

Didn't know I could do that. Will research more.

Tiff conversion worries me because of size. many Tiff files end up 20-60MB. The book has 350 photos. as is it is about 400 MB document. Putting in all pix as TIFFS would make it HUGE. Would that be a problem?

[Kees Sprengers]

Ken: >We supply 8-bit TIFF files in CMYK to our printers on the high end jobs. If you open your sRGB JPEG, convert it to the appropriate CMYK profile for the press conditions, then save it as a TIFF, you won't lose any quality due to re-compression of the JPEG.<

Thank you, appreciate the feedback. This is the first book we print, teething problms.

My worry is the total size of the final document. That became an issue when we were planning to print via LULU or BLURB, and would have to send the document via the net to the USA to be printed. Re issuing the 350 jpgs (average 3050k to 2 Mb each) as TIFFS (20MB to 60 MB each) would inflate the total document from 400 Mb total (with jpegs0 to much bigger with Tiffs.

Then again, NOT sending the final document to the printer by internet, but carrying it on a DVD (capacity 4.7 GB) or a USB stick (16 GB), that may not be an issue.

Thank you, I need to think about this more.

[deanwork]

I too would save it as a pdf directly from its source. However, saving a cmyk Tiff produces a much smaller file than an RGB Tiff. You do want to find out first what kind of cymk profile they need. Saving to an inappropriate cymk format can throw away information and create out of gamut colors for the press. There is no one type of offset press. Talk to your printer before doing anything.

There are even many shops that prefer to convert to the print space themselves.

j

[JohnKoerner]

I too would save it as a pdf directly from its source. However, saving a cmyk Tiff produces a much smaller file than an RGB Tiff. You do want to find out first what kind of cymk profile they need. Saving to an inappropriate cymk format can throw away information and create out of gamut colors for the press. There is no one type of offset press. Talk to your printer before doing anything.
There are even many shops that prefer to convert to the print space themselves.
j

+ 1 on the idea of just converting the In-Design document to .pdf and letting the Adobe conversion process do all the work of converting sRGB to CMYK. It would be a horrendous job to individually re-convert each and every photo from sRGB to CMYK. One thing I think you're mistaken on is the idea that the original photos will in any way be affected. If he exports the .idd to .pdf the original photos are unaffected; they are simply duplicated and re-saved in another file type.

To the original poster: Just open your In-Design document and click "File" on your menu. Scroll down to "export" and export your .idd document as a .pdf document. When you do this, hit "save" and then a new screen will pop up and give you many different options on a left column. One of these options will say "output," and when you click this you will see "color conversion" and you can click that and scroll the conversion to the appropriate CMYK output.

This is a far better and more sensible approach to your problem than opening, altering, and re-saving each and every photo---in fact, that's why the function exists (to save you the time)---so by all means use it

Good luck with your project!

Jack



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[papa v2.0]

Hi another thought.

Find out what is the optimum resolution the files need to be.

For example, if the book is being printed litho the files should be 300dpi as a rule of thumb.

If its being printed on a digital press (Xerox igen for example) the resolution required my be less, say 200dpi (i need to check this)

so if the required resolution is say 220dpi the files can be down-sampled when producing the .pdf at the same time as rgb to cmyk.

One drawback is loss of applied sharpening.  

This will reduce overall final document file size.

What dpi are the images at the moment?

[Kees Sprengers]

Hi another thought.

Find out what is the optimum resolution the files need to be.

For example, if the book is being printed litho the files should be 300dpi as a rule of thumb.

If its being printed on a digital press (Xerox igen for example) the resolution required my be less, say 200dpi (i need to check this)

so if the required resolution is say 220dpi the files can be down-sampled when producing the .pdf at the same time as rgb to cmyk.

One drawback is loss of applied sharpening.  

This will reduce overall final document file size.

What dpi are the images at the moment?

Thank you, i'll do that. Currently files are all 300 or a bit higher.